:root{--bg-primary: #0f1117;--bg-secondary: #161822;--bg-tertiary: #1e2030;--bg-card: #1a1c2e;--bg-card-hover: #222440;--bg-sidebar: #12131f;--border-color: #2a2d3e;--border-light: #353849;--text-primary: #e4e6f0;--text-secondary: #9ca0b0;--text-muted: #6b7084;--accent: #6366f1;--accent-light: #818cf8;--accent-glow: rgba(99, 102, 241, .15);--green: #22c55e;--green-bg: rgba(34, 197, 94, .1);--yellow: #f59e0b;--yellow-bg: rgba(245, 158, 11, .1);--red: #ef4444;--red-bg: rgba(239, 68, 68, .1);--blue: #3b82f6;--blue-bg: rgba(59, 130, 246, .1);--purple: #a78bfa;--sidebar-width: 340px;--header-height: 64px;--radius-sm: 6px;--radius-md: 10px;--radius-lg: 16px;--shadow-sm: 0 1px 3px rgba(0, 0, 0, .3);--shadow-md: 0 4px 12px rgba(0, 0, 0, .4);--shadow-lg: 0 8px 30px rgba(0, 0, 0, .5);--transition: .2s cubic-bezier(.4, 0, .2, 1)}[data-theme=light]{--bg-primary: #f8f9fc;--bg-secondary: #ffffff;--bg-tertiary: #f0f1f5;--bg-card: #ffffff;--bg-card-hover: #f5f6fa;--bg-sidebar: #ffffff;--border-color: #e2e4ec;--border-light: #ecedf3;--text-primary: #1a1c2e;--text-secondary: #5a5e72;--text-muted: #8c90a4;--accent-glow: rgba(99, 102, 241, .08);--shadow-sm: 0 1px 3px rgba(0, 0, 0, .06);--shadow-md: 0 4px 12px rgba(0, 0, 0, .08);--shadow-lg: 0 8px 30px rgba(0, 0, 0, .1)}*{margin:0;padding:0;box-sizing:border-box}html{font-size:15px;scroll-behavior:smooth}body{font-family:Inter,-apple-system,BlinkMacSystemFont,sans-serif;background:var(--bg-primary);color:var(--text-primary);display:flex;min-height:100vh;overflow-x:hidden}#root{display:flex;width:100%;min-height:100vh}::-webkit-scrollbar{width:6px}::-webkit-scrollbar-track{background:transparent}::-webkit-scrollbar-thumb{background:var(--border-color);border-radius:3px}::-webkit-scrollbar-thumb:hover{background:var(--text-muted)}.sidebar{width:var(--sidebar-width);height:100vh;position:fixed;top:0;left:0;background:var(--bg-sidebar);border-right:1px solid var(--border-color);display:flex;flex-direction:column;z-index:100;transition:transform .3s ease}.sidebar-header{display:flex;align-items:center;justify-content:space-between;padding:16px 20px;border-bottom:1px solid var(--border-color)}.logo{display:flex;align-items:center;gap:10px}.logo-text{font-size:1.1rem;font-weight:700;background:linear-gradient(135deg,var(--accent),var(--purple));-webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text}.sidebar-close{display:none;background:none;border:none;color:var(--text-muted);cursor:pointer;padding:4px;border-radius:var(--radius-sm);transition:var(--transition)}.sidebar-close:hover{color:var(--text-primary);background:var(--bg-tertiary)}.sidebar-search{padding:12px 16px;position:relative}.search-icon{position:absolute;left:28px;top:50%;transform:translateY(-50%);color:var(--text-muted);pointer-events:none}.sidebar-search input{width:100%;padding:10px 12px 10px 38px;background:var(--bg-tertiary);border:1px solid var(--border-color);border-radius:var(--radius-md);color:var(--text-primary);font-family:inherit;font-size:.87rem;outline:none;transition:var(--transition)}.sidebar-search input::placeholder{color:var(--text-muted)}.sidebar-search input:focus{border-color:var(--accent);box-shadow:0 0 0 3px var(--accent-glow)}.sidebar-stats{display:grid;grid-template-columns:repeat(3,1fr);gap:8px;padding:8px 16px 4px}.stat-card{text-align:center;padding:8px 4px;background:var(--bg-tertiary);border-radius:var(--radius-sm);border:1px solid var(--border-color)}.stat-number{display:block;font-size:1.1rem;font-weight:700;color:var(--accent-light);font-family:JetBrains Mono,monospace}.stat-label{font-size:.7rem;color:var(--text-muted);text-transform:uppercase;letter-spacing:.5px}.progress-bar-container{margin:8px 16px;height:4px;background:var(--bg-tertiary);border-radius:2px;overflow:hidden}.progress-bar{height:100%;width:0%;background:linear-gradient(90deg,var(--accent),var(--purple));border-radius:2px;transition:width .5s ease}.difficulty-filter{display:flex;gap:6px;padding:8px 16px 12px}.filter-btn{flex:1;padding:6px 8px;background:var(--bg-tertiary);border:1px solid var(--border-color);border-radius:var(--radius-sm);color:var(--text-muted);font-size:.75rem;font-weight:600;font-family:inherit;cursor:pointer;transition:var(--transition)}.filter-btn:hover{color:var(--text-primary);border-color:var(--border-light)}.filter-btn.active{background:var(--accent);border-color:var(--accent);color:#fff}.sidebar-nav{flex:1;overflow-y:auto;padding:4px 12px 20px}.nav-category{margin-bottom:2px}.nav-category-header{display:flex;align-items:center;gap:10px;padding:10px 12px;border-radius:var(--radius-md);cursor:pointer;transition:var(--transition);border:none;background:none;width:100%;text-align:left;color:var(--text-primary);font-family:inherit}.nav-category-header:hover{background:var(--bg-tertiary)}.nav-category-header.active{background:var(--accent-glow);border-left:3px solid var(--accent)}.category-icon{width:32px;height:32px;display:flex;align-items:center;justify-content:center;border-radius:var(--radius-sm);font-size:1rem;flex-shrink:0}.nav-category-info{flex:1;min-width:0}.nav-category-name{font-size:.85rem;font-weight:600;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}.nav-category-count{font-size:.72rem;color:var(--text-muted);margin-top:1px}.nav-category-progress{width:36px;height:36px;position:relative;flex-shrink:0}.nav-category-progress svg{transform:rotate(-90deg)}.nav-category-progress .progress-text{position:absolute;top:0;right:0;bottom:0;left:0;display:flex;align-items:center;justify-content:center;font-size:.6rem;font-weight:700;font-family:JetBrains Mono,monospace;color:var(--text-secondary)}.nav-problems{overflow:hidden;max-height:0;transition:max-height .3s ease}.nav-problems.expanded{max-height:2000px}.nav-problem-item{display:flex;align-items:center;gap:8px;padding:7px 12px 7px 54px;cursor:pointer;border-radius:var(--radius-sm);transition:var(--transition);font-size:.8rem;color:var(--text-secondary)}.nav-problem-item:hover{background:var(--bg-tertiary);color:var(--text-primary)}.nav-problem-item.solved{color:var(--green)}.nav-problem-check{width:16px;height:16px;border:1.5px solid var(--border-light);border-radius:4px;display:flex;align-items:center;justify-content:center;flex-shrink:0;transition:var(--transition);cursor:pointer}.nav-problem-check:hover{border-color:var(--accent)}.nav-problem-item.solved .nav-problem-check{background:var(--green);border-color:var(--green)}.nav-problem-check svg{opacity:0;transition:var(--transition)}.nav-problem-item.solved .nav-problem-check svg{opacity:1}.nav-problem-name{flex:1;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}.nav-problem-diff{font-size:.65rem;padding:2px 6px;border-radius:3px;font-weight:600;flex-shrink:0}.nav-problem-diff.Easy{color:var(--green);background:var(--green-bg)}.nav-problem-diff.Medium{color:var(--yellow);background:var(--yellow-bg)}.nav-problem-diff.Hard{color:var(--red);background:var(--red-bg)}.main-content{flex:1;margin-left:var(--sidebar-width);min-height:100vh;display:flex;flex-direction:column}.main-header{height:var(--header-height);display:flex;align-items:center;gap:16px;padding:0 28px;border-bottom:1px solid var(--border-color);background:var(--bg-secondary);position:sticky;top:0;z-index:50;-webkit-backdrop-filter:blur(12px);backdrop-filter:blur(12px)}.hamburger{display:none;background:none;border:none;color:var(--text-secondary);cursor:pointer;padding:6px;border-radius:var(--radius-sm)}.hamburger:hover{background:var(--bg-tertiary);color:var(--text-primary)}.page-title{flex:1;font-size:1.15rem;font-weight:700}.header-actions{display:flex;align-items:center;gap:8px}.theme-toggle{background:var(--bg-tertiary);border:1px solid var(--border-color);border-radius:var(--radius-sm);color:var(--text-secondary);cursor:pointer;width:36px;height:36px;display:flex;align-items:center;justify-content:center;transition:var(--transition)}.theme-toggle:hover{color:var(--text-primary);border-color:var(--accent)}.moon-icon{display:block}.sun-icon,[data-theme=light] .moon-icon{display:none}[data-theme=light] .sun-icon{display:block}.welcome-view{padding:40px 28px;max-width:1200px;width:100%;margin:0 auto}.welcome-hero{text-align:center;padding:40px 20px;margin-bottom:36px}.hero-icon{margin-bottom:20px;animation:float 3s ease-in-out infinite}@keyframes float{0%,to{transform:translateY(0)}50%{transform:translateY(-8px)}}.welcome-hero h2{font-size:2rem;font-weight:800;margin-bottom:12px;background:linear-gradient(135deg,var(--text-primary),var(--accent-light));-webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text}.welcome-hero p{font-size:1.05rem;color:var(--text-secondary);max-width:600px;margin:0 auto;line-height:1.7}.roadmap-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(240px,1fr));gap:12px;margin-bottom:40px}.roadmap-card{background:var(--bg-card);border:1px solid var(--border-color);border-radius:var(--radius-lg);padding:20px;cursor:pointer;transition:var(--transition);position:relative;overflow:hidden}.roadmap-card:before{content:"";position:absolute;top:0;left:0;right:0;height:3px;background:var(--card-accent, var(--accent));opacity:0;transition:var(--transition)}.roadmap-card:hover{border-color:var(--border-light);transform:translateY(-2px);box-shadow:var(--shadow-md)}.roadmap-card:hover:before{opacity:1}.roadmap-card-icon{font-size:1.5rem;margin-bottom:12px}.roadmap-card h3{font-size:.95rem;font-weight:700;margin-bottom:6px}.roadmap-card-meta{display:flex;align-items:center;gap:8px;font-size:.78rem;color:var(--text-muted);margin-bottom:10px}.roadmap-card-bar{height:3px;background:var(--bg-tertiary);border-radius:2px;overflow:hidden}.roadmap-card-bar-fill{height:100%;background:var(--card-accent, var(--accent));border-radius:2px;transition:width .5s ease}.quick-tips{margin-top:20px}.quick-tips h3{font-size:1.2rem;font-weight:700;margin-bottom:16px}.tips-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(220px,1fr));gap:12px}.tip-card{background:var(--bg-card);border:1px solid var(--border-color);border-radius:var(--radius-md);padding:20px}.tip-icon{width:32px;height:32px;display:flex;align-items:center;justify-content:center;background:var(--accent-glow);color:var(--accent-light);border-radius:var(--radius-sm);font-weight:800;font-size:.85rem;margin-bottom:12px}.tip-card h4{font-size:.9rem;font-weight:700;margin-bottom:6px}.tip-card p{font-size:.82rem;color:var(--text-secondary);line-height:1.5}.category-view{padding:28px;max-width:960px;width:100%;margin:0 auto}.category-header-card{background:var(--bg-card);border:1px solid var(--border-color);border-radius:var(--radius-lg);padding:28px;margin-bottom:24px;position:relative;overflow:hidden}.category-header-card:before{content:"";position:absolute;top:0;left:0;right:0;height:4px;background:linear-gradient(90deg,var(--accent),var(--purple))}.category-meta{display:flex;align-items:center;gap:12px;margin-bottom:12px}.category-badge{font-size:.72rem;font-weight:700;text-transform:uppercase;letter-spacing:.5px;padding:4px 10px;background:var(--accent-glow);color:var(--accent-light);border-radius:4px}.category-progress-text{font-size:.82rem;color:var(--text-muted);font-family:JetBrains Mono,monospace}.category-view h2{font-size:1.5rem;font-weight:800;margin-bottom:8px}.category-view .category-header-card>p{color:var(--text-secondary);font-size:.9rem;line-height:1.6;margin-bottom:16px}.category-progress-bar{height:6px;background:var(--bg-tertiary);border-radius:3px;overflow:hidden;margin-bottom:16px}.category-progress-fill{height:100%;background:linear-gradient(90deg,var(--accent),var(--purple));border-radius:3px;transition:width .5s ease}.pattern-tags{display:flex;flex-wrap:wrap;gap:6px}.pattern-tag{font-size:.72rem;padding:4px 10px;background:var(--bg-tertiary);border:1px solid var(--border-color);border-radius:20px;color:var(--text-secondary)}.problems-list{display:flex;flex-direction:column;gap:8px}.problem-card{background:var(--bg-card);border:1px solid var(--border-color);border-radius:var(--radius-md);padding:16px 20px;display:flex;align-items:center;gap:14px;cursor:pointer;transition:var(--transition)}.problem-card:hover{border-color:var(--border-light);background:var(--bg-card-hover);transform:translate(4px)}.problem-card.solved{border-left:3px solid var(--green)}.problem-checkbox{width:22px;height:22px;border:2px solid var(--border-light);border-radius:6px;display:flex;align-items:center;justify-content:center;flex-shrink:0;cursor:pointer;transition:var(--transition)}.problem-checkbox:hover{border-color:var(--accent);background:var(--accent-glow)}.problem-card.solved .problem-checkbox{background:var(--green);border-color:var(--green)}.problem-checkbox svg{color:#fff;opacity:0;transition:var(--transition)}.problem-card.solved .problem-checkbox svg{opacity:1}.problem-info{flex:1;min-width:0}.problem-number{font-size:.72rem;color:var(--text-muted);font-family:JetBrains Mono,monospace;margin-bottom:2px}.problem-name{font-size:.92rem;font-weight:600}.problem-tags-row{display:flex;gap:6px;margin-top:4px;flex-wrap:wrap}.problem-tag{font-size:.65rem;padding:2px 6px;background:var(--bg-tertiary);border-radius:3px;color:var(--text-muted)}.problem-actions{display:flex;align-items:center;gap:8px;flex-shrink:0}.difficulty-badge{font-size:.75rem;font-weight:600;padding:4px 10px;border-radius:var(--radius-sm)}.difficulty-badge.Easy{color:var(--green);background:var(--green-bg)}.difficulty-badge.Medium{color:var(--yellow);background:var(--yellow-bg)}.difficulty-badge.Hard{color:var(--red);background:var(--red-bg)}.problem-link{display:inline-flex;align-items:center;gap:4px;font-size:.78rem;color:var(--accent-light);text-decoration:none;padding:4px 10px;border:1px solid var(--border-color);border-radius:var(--radius-sm);transition:var(--transition)}.problem-link:hover{background:var(--accent-glow);border-color:var(--accent)}.problem-view{padding:28px;max-width:960px;width:100%;margin:0 auto}.back-btn{display:inline-flex;align-items:center;gap:6px;padding:8px 14px;background:var(--bg-tertiary);border:1px solid var(--border-color);border-radius:var(--radius-sm);color:var(--text-secondary);font-family:inherit;font-size:.82rem;cursor:pointer;transition:var(--transition);margin-bottom:20px}.back-btn:hover{color:var(--text-primary);border-color:var(--accent)}.problem-detail{background:var(--bg-card);border:1px solid var(--border-color);border-radius:var(--radius-lg);padding:28px;margin-bottom:20px}.problem-detail h2{font-size:1.4rem;font-weight:800;margin-bottom:8px}.problem-detail-meta{display:flex;align-items:center;gap:10px;margin-bottom:16px;flex-wrap:wrap}.problem-detail-desc{color:var(--text-secondary);line-height:1.7;font-size:.92rem;margin-bottom:16px}.problem-detail-approach h3{font-size:1rem;font-weight:700;margin-bottom:8px;color:var(--accent-light)}.problem-detail-approach p{color:var(--text-secondary);line-height:1.6;font-size:.88rem}.problem-detail-approach ul{list-style:none;padding:0;margin:8px 0}.problem-detail-approach 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h3{font-size:1rem;font-weight:700;margin-bottom:16px}.viz-container{display:flex;flex-direction:column;align-items:center;gap:20px}.viz-array{display:flex;gap:4px;flex-wrap:wrap;justify-content:center}.viz-cell{width:44px;height:44px;display:flex;align-items:center;justify-content:center;background:var(--bg-tertiary);border:2px solid var(--border-color);border-radius:var(--radius-sm);font-weight:600;font-family:JetBrains Mono,monospace;font-size:.85rem;transition:all .3s ease}.viz-cell.highlight{border-color:var(--accent);background:var(--accent-glow);color:var(--accent-light)}.viz-cell.found{border-color:var(--green);background:var(--green-bg);color:var(--green)}.viz-cell.pointer-left{border-color:var(--blue);background:var(--blue-bg);color:var(--blue)}.viz-cell.pointer-right{border-color:var(--purple);background:#a78bfa26;color:var(--purple)}.viz-controls{display:flex;gap:8px;align-items:center}.viz-btn{padding:8px 16px;background:var(--accent);border:none;border-radius:var(--radius-sm);color:#fff;font-family:inherit;font-size:.82rem;font-weight:600;cursor:pointer;transition:var(--transition)}.viz-btn:hover{background:var(--accent-light)}.viz-btn.secondary{background:var(--bg-tertiary);border:1px solid var(--border-color);color:var(--text-secondary)}.viz-btn.secondary:hover{color:var(--text-primary);border-color:var(--accent)}.viz-step-info{text-align:center;color:var(--text-secondary);font-size:.88rem;line-height:1.5;padding:12px;background:var(--bg-tertiary);border-radius:var(--radius-sm);width:100%;max-width:500px}.viz-step-info code{font-family:JetBrains Mono,monospace;background:var(--bg-primary);padding:2px 6px;border-radius:3px;font-size:.82rem;color:var(--accent-light)}.viz-linked-list{display:flex;align-items:center;gap:0;flex-wrap:wrap;justify-content:center}.viz-node{display:flex;align-items:center}.viz-node-box{width:48px;height:48px;display:flex;align-items:center;justify-content:center;background:var(--bg-tertiary);border:2px solid var(--border-color);border-radius:var(--radius-sm);font-weight:600;font-family:JetBrains Mono,monospace;font-size:.9rem;transition:all .3s ease}.viz-arrow{width:28px;display:flex;align-items:center;justify-content:center;color:var(--text-muted);font-size:.85rem}.viz-tree{display:flex;flex-direction:column;align-items:center;gap:8px}.viz-tree-level{display:flex;gap:16px;justify-content:center}.viz-tree-node{width:42px;height:42px;display:flex;align-items:center;justify-content:center;background:var(--bg-tertiary);border:2px solid var(--border-color);border-radius:50%;font-weight:600;font-family:JetBrains Mono,monospace;font-size:.85rem;transition:all .3s 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h2{font-size:1.5rem}.roadmap-grid,.tips-grid{grid-template-columns:1fr}.problem-card{flex-wrap:wrap}.problem-actions{width:100%;justify-content:flex-end}}@media(max-width:480px){.main-header{padding:0 16px}.welcome-view,.category-view,.problem-view{padding:16px}.sidebar-stats{grid-template-columns:repeat(3,1fr)}}@keyframes fadeSlideIn{0%{opacity:0;transform:translateY(8px)}to{opacity:1;transform:translateY(0)}}